Mechanism of Spontaneous Autogamy in the Allogamous Lepidopteran Orchid Gymnadenia Conopsea (L.) R. Br. (Orchidaceae)

Studies of plant breeding systems are particularly important when they involve facultative processes, which can be overlooked in natural conditions. This especially applies to species that are considered allogamous, due to their pollination syndrome and floral architecture. We examined the potential level and factors enabling or limiting spontaneous autogamy in three populations of the lepidopteran orchid Gymnadenia conopsea. Using a bagging experiment, we noted the stages of the anther thecae and the positions of the pollinaria at the five phenological stages of the flower, as well as the quantity of autogamously set fruits and the number of properly formed seeds. In the studied populations, autogamy represents an accidental character, with a maximum of 3.3% of fruits set spontaneously per analysed sample in a given population, and with seed numbers ranging from 29 to 354. This process is an environmentally dependent co-product of the mechanisms that enable a position appropriate for touching the stigma (bending of the caudicle) and increase male fitness (disintegration of the massulae), preceded by the gradual opening of the anther chambers. Autopollination of G. conopsea may occur in the flowers at various flowering stages (excluding the beginning of anthesis) at each position on the inflorescence.